56 
BULLETIN 1026, U. S. DEPARTMENT OF AGRICULTURE. 
conditions are different and when water is plentiful the safe opera- 
tion of the canal requires that the user take his supply of water 
from the canal day and night until he orders it cut off by the ditch 
rider. When water is scarce the user takes it eagerly, day or night. 
It is necessity in these forms, rather than any virtue in its practice 
in the Cache la Poudre Valley, which is responsible for night irri- 
gation there. Row crops are not often irrigated at night and mat- 
ters are usually so arranged that the supply may be turned for the 
night on alfalfa or pasture land where a small excess of water will 
do no harm. 
i 
\PRIL 
20 
MAY 
10 20 
JUNE 
20 
1 
JULY 
20 
AUGUST 
10 20 
SEPTEMBER 
10 20 
19 
16 
_i 
.ll 
L 
1 
k 
d 
IV 
v\ 
k 
1 
d 
A* 
: m 
^ 
k 
o 
fc 10 
19 
17 
<0 
Is 
t 
f. Ii 
j 
I 
mm 
_|_ 
I il 
I 

££ 
14 J 
1 
m 
ill 
n 
Fl 
G. 8 
.—i 
rrigt 
Ltion 
of 
poto 
itoes 
and 
. V 
285 
Pate 
acr 
- re 
es ii 
guire 
L 19J 
imen 
7. 
ts 
f n 
57 a 
eres 
in 
1916 
It is seldom possible to apply enough water to a field for a 
uniform, thorough irrigation without having a certain run-off at the 
lower end. The amount of this run-off was determined for a num- 
ber of fields of alfalfa and grain and was found to range from 2 to 
18 per cent, with an average slightly under 6 per cent. In the 
majority of cases this can be called waste only with reference to the 
particular field from which it comes as the general practice is to 
collect it in ditches and use it on lower fields. 
In figure 4 the relation between the head used and the area irri- 
gated per 24-hour day is shown by curves for both flood and furrow 
irrigation. The curve for flood irrigation is based on 284 irriga- 
tions of fields of alialf a and grain, while the curve for furrow ii ri- 
